N-methyl-n-phenyl-n-(3,5-di-tertiary-butyl-4-hydroxybenzyl)amine



United States Patent 3,225,099 N-METHYL-N-PHENYL-N-(3,5-DI-TERTIARY- BUTYL-4-HYDROXYBENZYL)ANHNE Thomas H. Coflield, Farmington, Mich., assignor to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed Dec. 3, 1964, Ser. No. 415,783 1 Claim. (Cl. 260570.9)

This application is a continuation-in-part of application Serial No. 71,879, filed November 28, 1960, now abandoned, which in turn is a continuation-in-part of application Serial No. 536,316, filed September 23, 1955, now US. Patent No. 2,962,531, issued November 29, 1960.

This invention relates to novel chemical compounds having utility in the chemical arts.

In particular, this invention relates to novel 3,5-dialkyl-4-hydroxybenzyl amines which are eminently suited for use as antioxidants.

Among the objects of this invention is that of providing new chemical compounds useful for the above and other purposes. Another object is to provide methods of preparing these new chemical compounds. Another object is to provide hydrocarbon oil normally tending to deteriorate in the presence of oxygen containing these new compounds in amount suflicient to inhibit this deteriorat-ion. Another object is to provide lubricating oil and greases normally tending to deteriorate in the presence of oxygen containing, in amount suflicient to inhibit such deterioration, a small antioxidant quantity of novel and highly effective antioxidants. Still another object is to provide turbine and other industrial oils stabilized against oxidative deterioration by the presence therein of a small antioxidant quantity of novel and highly effective antioxidants. Other objects will be apparent from the ensuing description.

The above and other objects of this invention are accomplished by providing as new compositions of matter 3,5-dialkyl-4-hydroxybenzyl amines having the general formula:

wherein R is an alkyl group containing from 1 to 12 carbon atoms, R is an alkyl group containing from 3 to 12 carbon atoms which is branced on the alpha carbon atom, R is selected from the group consisting of alkyl, cycloalkyl, aralkyl, aryl, alkaryl and HOQCHP and R is selected from the group consisting of hydrogen, alkyl, cycloalkyl, aralkyl, aryl and alkaryl. In the above compounds it is preferable that the hydrocarbon radicals of the groups designated above as R and R contain the following ranges of carbon atoms: alkyl, 1 to 12; cycloalkyl, 5 to 6; aralkyl, 7 to 11; aryl, 6 to and alkaryl, 7 to 15.

A preferred embodiment of this invention relates to 3,5-dialkyl-4-hydroxybenzyl amines in which at least one of R and R is an alkyl group as above-defined. The compounds of this embodiment are more effective antioxidants for oxygen-sensitive oils than are the remainder of the compounds of this invention.

Another preferred embodiment of this invention are 3,5-dialkyl-4-hydroxybenzyl amines in which at least one 3,225,999 Patented Dec. 21, 1965 of R and R is an alkyl group as above-defined and R and R are both tertiary alkyl groups containing from 4 to 12 carbon atoms. These latter compounds possess outstanding effectiveness as antioxidants for a wide variety of oxygen-sensitive oils, such as lubricating oil, transformer oil, turbine oil, gear oil and the like.

A particularly preferred embodiment of this invention is compounds described above in which R and R are tertiary butyl groups, and in which at least one of R and R is a lower alkyl group, that is an alkyl group containing from 1 to 6 carbon atoms.

The most particularly preferred embodiment of this invention is compounds described above in which R and R are tertiary butyl groups, R is a lower alkyl group, that is an alkyl group containing from 16 carbon atoms, and R is selected from the group consisting of hydrogen and benzene. These compounds are most particularly preferred because they are eminently effective as antioxidants, having effect in a wide range of media, such as lubricating oil, transformer oil, turbine oil, gear oil, grease and rubber.

Typical compounds of this invention include: N-cyclohexyl N- 3-methyl-S-isopropyl-4-hydroxybenzyl amine, N benzyl-N-(3,5-diisopropyl-4-hydroxybenzyl) amine, N- benzyl-N-(3,5-di-tert-butyl-4 hydroxybenzy1)amine, N phenyl-N-(3-methyl-5-(2-octyl)-4 hydroxybenzyl) amine, N 3(3,S xylyl)-N-(3,S-di-tert-amyl-4-hydroxybenzyl)- amine, N cyclohexyl N,N bis (3,5-diisopropyl-4-hydroxybenzyl)amine, N (p-butylbenzyl)-N,N-bis-(3,5-ditert-butyl-4-hydroxybenzyl)amine, N benzyl-N,N-bis-(3- methyl-5-(1,1,3,3-tetramethyl-butyl) 4 hydroxybenzyl)- amine, N (a-naphthyl) -N,N-bis-(3,5-diisopropyl-4-hydroxybenzyl)amine, N (p-tolyl)-N,N-bis-(3,5-di-(2-dodecyl)-4-hydroxybenzyl)amine, N,N di (phenyl)-N- (3,5-di-(2-hexyl)-4-hydroxybenzyl) amine, N phenyl N- (p-tolyl -N- 3 ,5 -di- (2-amyl) -4-'hydroxybenzyl) amine, N- (p octylphenyl) N (3-ethyl-5-tert-butyl-4-hydroxybenzyl)amine, and the like.

The first preferred embodiment of this invention as above-described is illustrated by such compounds as N- methyl N-(3,S-diisopropyl-4-hydroxybenzyl)amine, N octyl N (3-methyl-5-tert-butyl-4-hydroxybenzyl)amine, N (2-dodecyl)-N-(3,5-di-(2-hexyl)-4-hydroxybenzyl)- amine, N,N diethyl N (3-isopropyl-5-tert-butyl-4-hydroxybenzy1)amine, N,N di-butyl-N-(3,5-diisopropyl-4- hydroxybenzyl)amine, N methyl-N-ethyl-N-(3,5-di-(2- octyl)-4-hydroxybenzyl)amine, N sec-butyl-N-dodecyl- N (3,5 diisopropyl-4-hydroxybenzyl)amine, N-propyl- N,N bis-(3-methyl-5-tert-butyl-4-hydroxybenzyl)amine, N (sec amyl)-N,N-bis-(3,5-di-sec-butyl-4-hydroxybenzyl)amine, N decyl N,N-bis-(3-ethyl-5-(3-decyl)-4-hydroxybenzyl)amine, and the like.

The second preferred embodiment of this invention is illustrated by such compounds as N-heptyl-N- 3,5 -di-tert-butyl-4-hydroxybenzl) amine,

N-isopropyl-N- 3 ,5 -di-tertamyl-4-hydroxybenzyl amine,

N-nonyl-N- 3-tert-butyl-S-tert-amyl-4-hydroxybenzyl) amine;

N-N-diisobutyl-N- (3 ,5 -di-tert-amyl-4-hydroxybenzyl amine;

N,N-dioctyl-N- (3 ,5 -di-( 1, l ,3,3-tetramethylbutyl) -4-hydroxybenzyl) amine;

N-propyl-N-amyl-N- 3 ,5-di-(1,1,2,2,-tetramethylpropyl)- 4 -hydroxybenzyl) amine;

N-me thyl-N-,N-bis- (3 ,5 ,-di-tert-amyl-4-hydroxybenzyl) amine;

N-heptyl-N-,N-bis- 3 ,5-di-tert-amyl-4-hydroxybenzyl) amine;

N-undecyl-N-N-bis- 3-tert-butyl-5-tert-amyl-4-hydroxybenzyl) amine, and the like.

4.3 The particularly preferred embodiment of this invention comprises such compounds as N-methyl-N- 3 ,5 ,-ditert-butyl-4-hydroxybenzyl) amine;

N-ethyl-N- 3,S-di-tert-butyl-4-hydroxybenzyl amine;

N-butyl-N- (3 ,5 -di-tertbutyl-4-hydroxybenzyl) amine;

N-isohexyl-N- 3,5 -di-tert-butyl-4-hydroxybenzyl) amine;

N,N-dimethyl-N- 3,5-di-tert-butyl-4-hydroxybenzyl) amine;

N,N-di-propyl-N- (3 ,5 -di-tert-butyl-4-hydroxybenzyl) amine;

N-methyl-N-ethyl-N- 3, 5 -di-tert-butyl-4-hydroxybenzyl) amine;

N-ethyl-N,N-bis- 3, 5 -di-tert-butyl-4-hydroxybenzyl amine;

N-butyl-N,N-bis- 3 ,5 -di-tert-butyl-4-hydroxybenzyl) amine;

N-tert-amy1-N,Nbis3,5-di-tert-butyl-4-hydroxybenzyl) amine;

and the like.

The most particularly preferred embodiment of this invention comprises such compounds as N-methyl-N- (3 ,5-di-tert-butyl-4-hydroxybenzyl) amine;

N-ethyl-N- (3 ,5 -di-tert-butyl-4-hydroxybenzyl) amine N-butyl-N- (3 ,5 -di-tert-butyl-4-hydroxybenzyl) amine;

N-isohexyl-N- 3 ,5-di-tert-butyl-4-hydroxybenzyl) amine;

N-tert-butyl-N- 3,5,di-tert-butyl-4-hydroxybenzyl) amine;

N-n-hexyl-N-phenyl- 3,5-di-tert-butyl-4-hydroxybenzyl) amine; and

N-methyl-N-phenyl- 3 ,S-di-tert-butyl-4-hydroxybenzyl) amine.

The compounds of this invention are white or pale yellow crystalline solids and are soluble in various organic solvents and in gasolines, diesel fuels, hydrocar bon oils and the like. These compounds are further characterized by being relatively stable, easily crystalizable materials.

The compounds of this invention are prepared by reacting a 2,6-dialkyl phenol in which one of the alkyl groups contains from 3 to 12 carbon atoms and is branched on the alpha carbon atom and the other alkyl group contains from 1 to 12 carbon atoms; formaldehyde; and a primary or secondary amine in which the hydrocarbon portion thereof is in conformity with the groups designated hereinabove as R, and R In conducting this process a monohydric alcohol containing from 1 to 6 carbon atoms is preferably used as the reaction solvent. The reaction temperature is in the order of about 20 to about 100 C. It is preferred to conduct the process of this invention within the range of about 50 to 90 C.

In conducting this process the relative proportions of the three reactiants is varied depending upon the particular type of 3,5-dialkyl-4-hydroxybenzyl amine being prepared. Thus, when preparing the N,N-di-hydrocarbon substitute-N-(3,5-dialkyl-4-hydroxybenzyl)amines of this invention, one mole of formaldehyde and one mole of di-hydrocarbon substituted amine i.e., secondary amine-are employed per mole of appropriate 2,6-dialkyl phenol. When preparing N-hydrocarbon-N,N-bis-(3,5- dialkyl-4-hydroxybenzyl)amines of this invention, one mole of formaldehyde and one-half of a mole of monohydrocarbon substituted amine-i.e., primary amineare reacted per mole of appropriately substituted 2,6-dialkyl phenol used. When preparing the compounds of this invention which contain one hydrogen atom and one hydrocarbon group on the nitrogen atom, one mole of a formaldehyde and a large excess of primary amine are employed per mole of 2,6-dialkyl phenol used. This substantial excess of primary amine is in the order of about 8 to about 10 moles per mole of phenol used. This particular reaction is conducted in a large amount of mono-hydric alcohol solvent in order to achieve dilution of the reactants.

Thus, a facet of this invention is a process of preparing 3,5-dialkyl-4-hydroxybenzyl amines which comprises reacting a 2,6-dialkyl phenol in which one of the alkyl groups contains from 3 to 12 carbon atoms and is branched on its alpha carbon atom and the other alkyl group contains from 1 to 12 carbon atoms; formaldehyde; and an amine having the general formula wherein R is selected from the group consisting of alkyl containing from 1 to 12 carbon atoms, cycloalkyl containing from 5 to 6 carbon atoms, aralkyl containing from 7 to 11 carbon atoms, aryl containing from 6 to 10 carbon atoms and alkaryl containing from 7 to 15 carbon atoms and R is selected from the group consisting of hydrogen and R as just defined.

The compounds of this invention and the methods for their preparation are illustrated by the following specific examples wherein all parts and percentages are by weight.

EXAMPLE I In a reaction vessel equipped with stirring means, reflux means, thermometer and reagent introducing means were placed 89 parts of 2,6-diisopropylphenol, 248 parts of 25 percent aqueous dimethylamine solution and 500 parts of ethanol. To this solution was added parts of 37 per cent formalin solution at room temperature and the mixture refluxed for 4 hours at 83 C. The reaction mixture was then hydrolyzed with excess cold water and the solid product filtered off to give a 98 percent yield of N,Ndimethyl-N-(3,5-diisopropyl-4-hydroxybenzyl)amine, melting at 87 C. The analysis. Calculated for C H NO: 76.5 percent carbon, 10.7 percent hydrogen, and 5.95 percent nitrogen. Found: 77 percent carbon, 10.6 percent hydrogen, and 5.89 percent nitrogen.

EXAMPLE II In a reaction vessel equipped as described above, 103 parts of 2,6-di-tert-butylphenol, 248 parts of 25 percent aqueous dimethyl amine solution and 75 parts of 37 percent formalin solution were reacted at 75 C. in 500 parts of ethanol for 3 hours. The reaction mixture was then poured into excess cold water and the solid which formed filtered off to give a 98 percent yield of N,N- dimethyl-N- 3,5-tert-butyl-4-hydroxybenzyl) amine, melting point 92 C. The analysis.Calculated for C H NO: Carbon 77.51 percent, hydrogen 11.1 percent. Found: carbon 77.60 percent, hydrogen 11.0 percent.

EXAMPLE III In a reaction vessel equipped as in Example I were reacted 206 parts of 2,6-di-tert-butyl phenol, 38 parts of 40 percent aqueous methyl amine solution, 85 parts of 37 percent formalin solution in 500 parts of ethanol for three hours at 75 C. On cooling, the solid product precipitated out and was filtered off to give a 65 percent yield of N-methyl-N,N-bis-(3,5-di-tert-butyl-4-hydroxybenzyl)amine, melting point l7918l C. The analysis-Calculated for C H NO 79.63 percent carbon, 10.6 percent hydrogen. Found: 79.9 percent carbon and 10.3 percent hydrogen.

EXAMPLE IV Into the reaction equipment described in Example I are introduced 178 parts of 2,6-diisopropyl phenol, 38 parts of 40 percent aqueous methyl amine solution, 84 parts of a 37 percent aqueous solution of formalin and 500 parts of ethanol. These materials are then heated to a temperature of 70 C. On completion of the reaction, the mixture is poured into an excess of cold water and the solid materials which form are filtered off to give N-methyl-N,N-bis-(3,5-diisopropyl-4-hydroxy-. benzyl) amine.

EXAMPLE v In the reaction vessel of Example I are placed 159 parts of 2,6-di-(1,1,3,3-tetramethylbutyl)phenol, 45 parts of 37 percent aqueous formalin solution, 29 parts of 40 percent aqueous ethyl amine solution and 400 parts of methanol. This mixture is heated at 70 C. for 4 hours.

'On cooling and partially evaporating the solvent, N-ethyl- N,N-bis-(3,5-di-(1,1,3,3-tetramethylbutyl) 4 hydroxybenzyl)amine precipitates and is filtered 01f.

EXAMPLE VI In the reaction vessel of Example I are placed 15 parts of Z-methyl-6-isopropylphenol, 8.4 parts of 37 percent aqueous formalin solution, 77 parts of 40 percent aqueous methyl amine and 400 parts of ethanol. This mixture is stirred at 30 C. for 4 hours. The solvent is removed at reduced pressure with 25 mm. of mercury and the product crystallized from the residue. The prod- -.uct is N-methyl N (3 methyl 5 isopropyl-4 hydroxybenzyl)amine.

EXAMPLE VII N-octyl-N,N-bis-(3,5-di-tert-butyl 4 hydroxybenzyl) amine is prepared as follows: In the reaction vessel of Example I are placed 208 parts of 2,6-di-tert-butyl phenol, 85 parts of 37 percent aqueous formalin solution, 64 parts of octyl amine, and 500 parts of ethanol. This mixture is heated at 70 C. for 5 hours. On cooling and partially evaporating the solvent, the product is obtained as a crystalline solid.

EXAMPLE VIII Using 500 parts of ethanol as reaction solvent, N,N- dibenzyl N (3-isopropyl-5-tert-butyl-4-hydroxybenzyl) amine is prepared by reacting 97 parts of 2-isopropyl-6- tert-butyl phenol, 45 parts of 37 percent aqueous formalin solution and 98 parts of dibenzyl amine. The reaction is carried out at 70 C. for 4 hours. The product is recovered by partially evaporating the solvent and crystallizing the residual liquor.

EXAMPLE IX N-hexyl-'N,N-bis-(3,5-diisopropyl 4 hydroxybenzyl) amine is prepared in the reaction vessel of Example I from 178 parts of 2,6-diisopropyl phenol, 85 parts of 37 percent aqueous formalin solution, and 51 parts of hexyl amine using 600 parts of butanol as the solvent. The mixture is heated at 70 C. for 6 hours and poured into cold water. The product is filtered off as a crystalline solid.

EXAMPLE XI In the reaction vessel described in Example I are placed 89 parts of 2,6-di-tert-butyl phenol, 45 parts of 37 percent aqueous formalin solution, 65 parts of aniline hydrochloride and 800 parts of ethanol. This mixture is stirred at 70 C. for 12 hours and .poured into dilute sodium bicarbonate solution. N-phenyl N,N bis (3,5-di-tertbutyl-4-hydroxybenzyl)amine is filtered off as a crystalline solid.

EXAMPLE XII At a temperature of 65 C., 208 parts of 2,6-di-tertbutyl phenol, 85 parts of 37 percent aqueous formalin solution, and 130 parts of dibutyl amine are reacted in 700 parts of ethanol. After 4 hours, the reaction mixture is poured into cold water and the N,N-butyl-N-(3,5- di tert butyl 4 hydroxybenzyl) amine filtered oil as a white solid.

EXAMPLE XIII Using 700 parts of ethanol as reaction solvent, 215 parts of 2,6-di-(2-dodecyl)phenol, 45 parts of aqueous 37 percent formalin solution, and 143 parts of N-methyl aniline hydrochloride are heated for 5 hours at 70 C. The reaction mixture is poured into cold water and the N-methyl-N-phenyl N (3,5-di-(2-dodecyl)-4-hydroxybenzyl)amine crystallized from the insoluble residues.

EXAMPLE XIV N,N-diphenyl N (3-isopropyl-5-tert-butyl-4-hydroxybenzyl)amine is prepared by reacting 97 parts of 2-is0- propyl-6-tert-butyl phenol, 45 parts of 37 percent aqueous formalin solution, and 103 parts of diphenylamine hydrochloride in 800 milliliters of ethanol solvent. The reaction is carried out at 70 C. for 12 hours and then poured into cold water. The product is crystallized from the insoluble organic portion.

EXAMPLE XV Using 700 parts of ethanol as the solvent, N-methyl-N- fl-naphthyl-N-(3,5-diisopropyl-4-hydroxybenzyl)amine is prepared by reacting 89 parts of 2,6-diisopropylphenol, 45 parts of 37 percent aqueous formalin solution and 110 parts of N-methyl-fi-naphthyl amine hydrochloride. The reaction is carried out at 70 C. for 12 hours and then poured into cold dilute sodium bicarbonate solution. The product is then crystallized from the insoluble organic portion.

EXAMPLE XVI At 65 C, N,N dodecyl N (3,5 di tert butyl- 4-hydroxybenzyl)arnine is prepared by reacting 103 parts of 2,-6-di-tert-butyl)phenol, 45 parts of 37 percent aqueous formalin solution and I176 parts of di-dodecylamine for 6 hours. The reaction solvent used is 600 par-ts of ethanol. The product is obtained by pouring the reaction mixture into cold water, followed by crystallization of the insoluble organic residues from ligroin.

EXAMPLE XVII N. tert buty-l N (3,5 di tert butyl 4 -hydroxybenzyDamine is prepared by reacting 21 parts of 2,6-di-tert-butyl phenol, 8.4 parts of 37 percent aqueous formalin solution and 146 parts of tert-butyl amine. 1000 parts of ethanol is used as reaction solvent and the temperature is held at 30 C. for 4 hours. The solvent 'is evaporated at a pressure of 25 mm. of mercury and the residues poured into cold water. The product is crystallized from the insoluble organic portion.

EXAMPLE XVIII 211 parts of 2,6-di-tert-butyl phenol, 8.4 parts of 37 percent aqueous formalin solution, and parts of 2,6 diethyl aniline hydrochloride are stirred at 30 C. in 500 parts of ethanol for 12 hours. At the end of this time the solvent is evaporated at 30 mm. pressure of mercury and the residues Washed with cold water. The product is crystallized from the insoluble organic portion to provide white crystals of N-(2;6-diethyl phenyl)-N-(3,5-di-tertbutyl-4-hydroxybenzyl)amine.

EXAMPLE XIX 200 parts of 2,6-di-tert-butylphenol, 45 parts of aqueous, 37 percent formalin solution and 143 parts of N- methyl aniline hydrochloride are mixed in 700 parts of ethanol heated for 5 hours at 70 C. The reaction mixture is poured into cold water and the N-methyl-N- phenyl N 3,5 di tert butyl 4 hydroxybenzyl)- amine crystallized from the insoluble residues.

It can be seen from the above illustrative examples that the primary or secondary amines used in the reaction can also be used in the form of their hydrohalide salts. This practice is sometimes advantageous.

To illustrate the useful properties of the novel compounds of this invention, recourse is had to the Polyveriform oxidation stability test as described in the paper entitled Factors Causing Lubricating Oil Deterioration in Engines (Ind. and Eng. Chem., Anal. Ed. 17, 302. (1945)). See also A Bearing Corrosion Test for Lubricating Oils and Its Correlation With Engine Performance (Anal. Chem., 21, 737 (1949)). This test efiectively evaluates the performance of lubricating oil antioxidants. The test equipment, procedure employed and correlations of the results with engine performance are discussed in the first paper above cited. By employing various compounds of this invention in oxygen-sensitive lubricating oil, effective inhibition of oxidative deterioration is achieved.

Comparative tests were conducted using the method and apparatus essentially as described in the publication first above mentioned. One minor modification was that the steel sleeve and copper test piece described in this publication were omitted from the apparatus. In these tests an initially additive-free, 95 VI. solvent-refined SAE-IO crankcase oil was used. The principal test conditions consisted of passing 70 liters of air per hour through the test oil for a total period of 20 hours while maintaining the oil at a temperature of 280 F. Oxidative deterioration of the oil was further promoted by employing as oxidation catalysts 0.05 percent by weight of ferric oxide (as ferric Z-ethyl hexoate) and 0.10 percent by weight of lead bromide, both of these amounts being based upon the weight of oil employed. Various lubricating oils of this invention were prepared by blending small amounts of typical compounds of this invention with other individual portions of the above lubricating oil. These compositions were then subjected to the above stringent oxidation test. The results of these tests are shown in Table I.

Table I.-Eflect of Antioxidants an oxidation of lubricating oil Additive Viscosity Test Additive Cone Acid Increase N0. percent No. at 100 F.

by wt percent 1 None 5. 6 189 2 N ,N-dimethyl-N-(3,5-diisopropyl--hydroxybenzyl) amine 1. 2. 9 63 3 do s 2. 0 2. 0 51 4 N,N-dirncthyl-N-(3,5-ditertbutyl--hydroxy-benzyl) amine 1. 0 0. 27 8 5 d0 2. 0 0. 18 8 6 Ninethy1-N,N-bis(3,5-ditert butyl--h ydroxy-benzyl) amine 1. 0 0. 17 9 7 (10 2. 0 0. 12

By referring to the data presented in Table I, it is immediately apparent that the compounds of this invention effectively inhibit oxidative deterioration of lubricating oil.

To still further demonstrate the preeminence of the compounds of this invention as antioxidants for use in lubricating oil, another series of comparative tests was conducted. In this instance the test procedure used was essentially as described above with the exception that still more stringent test conditions were employed. These conditions were brought about by conducting the Polyveriforrn oxidation stability test at a temperature of 300 F. In these tests comparisons were made between a sample of the above described, additive-free crankcase lubricating oil and a separate portion of this oil with which had been blended 3 percent by weight of N,N-dimethyl N (3,5 di tert butyl 4 hydroxybenzyl)- amine. In Table II are shown the results of these tests.

8 Table II.Efiect of antioxidants on oxidation of lubricating oil It is clearly evident from the data shown in Table II that even under more stringent oxidizing conditions, the compounds of this invention (as reprcsented in this instance by N,N dimethyl N (3,5 di tert butyl 4 hydroxybenzyDamine'are outstanding antioxidants for antioxidants for oxygen-sensitive oils.

The compounds of this invention are particularly effective antioxidants for use in steam turbine oils. This is demonstrated by making use of the standard test procedure of the American Society for Testing Materials bearing ASTM designation D-943-54. According to thi test procedure, 300 milliliters of a suitable test oil is placed in contact with milliliters of water and the resulting oilwater system is maintained at a temperature of C. while passing oxygen therethrough at a rate of 3 liters per hour. Oxidation is catalyzed by the use of iron and copper wire. Periodically measurements are made of the acid number of the test oil and failure of an antioxidant is indicated by an acid number in excess of 2.0. It is found that when 1.0 weight percent of N-methyl-N-phenyl-(3,5-di-tert-butyl-4-hydroxybenzyl)amine is added to steam turbine oils, substantial resistance against oxidative deterioration results.

The compounds of this invention are very effective antioxidants for grease. The potency of the compounds of this invention in this respect i demonstrated by conducting the Norma-Hoffman Grease Oxidation Stability Test, ASTM test procedure D942-50. It is found that the presence of minor proportions of the compounds of this invention in conventional greases greatly inhibits oxidative deterioration. By way of example an initially antioxidant-free lithium base grease was modified to the extent that it contained 0.5 percent by weight of N-tert-bntyl-N- (3,5-di tert-butyl-4-hydroxybenzyl)amine and was subjected to the above oxidation stability test. It wa found that the presence of N-tert-butyl-N- (3,5-di=tert-butyl-4-hydroxybenzyl)amine greatly retarded oxygen absorption by the grease.

The results described above are merely illustrative of the efiectiveness of the compounds of this invention when employed as antioxidants. The compounds of this invention effectively inhibit oxidation in industrial lubricants of the hydrocarbon type, such as lubricating oil, turbine oil, transformer oil, transmission fluids, glass-annealing oil, gear and machine lubricants, hydraulic lubricants and other industrial oils, grease and the like. As pointed out above, the compounds of this invention as a class are effective antioxidants. Furthermore, the compounds of the various embodiments of this invention substantially differ in elfectiveness from one embodiment to another. For example, the compounds of the preferred class of this invention are more effective antioxidants than the compounds of this invention as a class. Still more effective are the particularly preferred compounds of this invention. The compounds of the most particularly preferred embodiment of this invention possesses still greater efliectiveness as antioxidants. In short, the compounds of the most particularly preferred embodiment of this invention are superlative antioxidants.

The compounds of this invention are also very effective antioxidants for high molecular weight hydrocarbon polymers, such as polyethylene, polystyrene, polyisobutylene,

9 rubber, butyl rubber, GRS rubber, GR-N rubber, methyl rubber, polybutene rubber, piperylene rubber, dimethyl butadiene rubber, and the like.

The compounds of this invention are also useful in protecting petroleum waxparafiin wax and micro-crystalline Waxagainst oxidative deterioration. The compounds of this invention also find use in the stabilization of edible fats and oils of animal or vegetable origin which tend to become rancid especially during long periods of storage because of oxidative deterioration. Typical representatives of these edible fats and oils are linseed oil, cod liver oil, castor oil, soybean oil, rapeseed oil, coconut oil, olive oil, palm oil, corn oil, sesame oil, peanut oil, babassu oil, butter, fat, lard, beef tallow, and the like. The cornpounds of this invention may also be used as antioxidants for gasolines containing lead alkyl antiknock agents, such as tetraethyllead; concentrated formulations of tetraalkyllead compounds, such as pure tetraetbyllead or te-traethyllead admixed with organic halogen scavengers, oxygensensitive diesel fuels, domestic heating oils, bunker and residual fuel oils, asphalt, and other organic material normally susceptible of oxidative deterioration.

The amounts of the compounds of this invention employed in the materials to be stabilized are dependent both upon the nature of the material itself and the oxidative conditions to be encountered. Generally speaking, amounts in the order of about 0.001 to about 3 percent by weight of the material to be protected are satisfactory. In some cases such as where the antioxidant is employed in an article normally subjected to severe oxidizing con ditions, somewhat higher concentrations are useful.

The 2,6-dialkyl phenols which are employed as starting materials in the preparation of the compounds of this invention can be prepared by alkylating a phenol or an appropriate mono ortho alkyl phenol with an olefinic hydrocarbon in the presence of an aluminum phenoxide catalyst.

In order to obtain comparative data on the effective ness of the claimed compound, N-phenyl-N-(3,5-di-tert 'butyl-4-=hydroxybenzyl)amine and N,N-dimethyl-N-(3,5 di-tert-buty1-4-hydroxybenzyl)amine, samples of oil containing these compounds were tested in tandard oil oxi dation tests.

The equipment and test procedure described by Kroger et al., Erdol and Kohle, 2, page 398 (1949), served as a basis for the tests. The equipment and procedures were slightly modified in order to make the oxidizing condi tions more strenuous. In this manner, the test lubricants were subjected to severe oxidizing conditions in order to conclusively establish the effectiveness of additives under very adverse conditions. Furthermore, the modifications are found to provide results which correlate extremely well with test results of other standard procedures, in cluding actual engine tests.

The equipment consisted of a reaction cell connected with an open end manometer whereby the total uptake of oxygen by the oil was determined by noting the drop in height of the mercury in the manometer. The test oil sample was placed in the reaction cell which was then flushed with oxygen. The temperature was raised and held at that selected for the test until the substrate oil underwent catastrophic oxidation which was shown by a rapid oxygen uptake. In all cases the test oil was deliberately con taminated with iron hexoate as an oxidation promoter. In tests of this nature, the oxidation stability of a test lubricant is determined by measuring its induction period; that is, the time required for catastrophic deterioration under the above outlined conditions.

One test sample contained 1.0 10- mole/liter of N- methyl N phenyl N (3,5 di tert butyl 4 hydroxybenzyl)amine and the other contained 1.0x l0 mole/liter of N,N dimet-hyl N (3,5 di tert butyl- 4-hydroxybenzyl)amine. Upon being subjected to the above test conditions the test oil containing N,N-dimethyl- N-(3,5-di-tert-butyl-4-hydroxybenzyl)amine had an induction period of 19-9 minutes while the test oil containing N methyl N phenyl N (3,5 di tert butyl- 4-hydroxybenzyl)amine had an induction time of 410 minutes.

It is clear from the above data that N-methyl-N-p-henyl- N- 3,5 -di-tert-butyl-4-hydroxybenzyl) amine is unexpectedly superior to N,N dimethyl N (3,5 di tert butyl- 4-hydroxybenzyl)amine as an oil antioxidant.

I claim:

N methyl N phenyl N (3,5 di tert butyl 4- hydroxybenzyDamine.

No references cited.

CHARLES B. PARKER, Primary Examiner. 

